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MEPS 518:153-163 (2015)  -  DOI:

Wave action limits crowding in an intertidal mussel

Jorge L. Gutiérrez1,2,3,*, M. Gabriela Palomo1,4, María Bagur4, Lorena P. Arribas4, Sabrina A. Soria

1Grupo de Investigación y Educación en Temas Ambientales (GrIETA), San Eduardo del Mar, Argentina
2Facultad de Ciencias Exactas y Naturales and CONICET, Universidad Nacional de Mar del Plata, Mar del Plata, Argentina
3Cary Institute of Ecosystem Studies, Millbrook, NY 12545, USA
4Museo Argentino de Ciencias Naturales ‘Bernardino Rivadavia’ (MACN-CONICET), Buenos Aires, Argentina
*Corresponding author:

ABSTRACT: Intraspecific competition for space is generally invoked as the chief process limiting crowding in sessile or highly sedentary marine invertebrates. However, the mechanisms by which high conspecific density induces individual removal or mortality, in turn restraining crowding in these organisms, generally remain uninvestigated. Here we illustrate that mussel crowding in a southwestern Atlantic rocky intertidal shore is limited by a combination of wave action and space limitation. Brachidontes rodriguezii mussel beds at this site occur primarily as a single layer of individuals because wave forces remove multilayered mussel hummocks quickly after they develop. Mussels in hummocks show lower attachment strength than those in the single-layered matrix. Accordingly, wave conditions associated with the passage of cold fronts (i.e. transition zones from warm air to cold air accompanied by moderate to strong winds and wave action, with 7 d average recurrence times based on historical weather data) cause detectable mussel dislodgment in a high proportion of hummocks but have virtually no impact on single-layered areas. Since wave action is the proximate cause of mussel dislodgment, upper limits to crowding in this species would not be fixed to a particular level of space occupation (i.e. as predictable from inter-individual interference alone) but would be variable in space and time depending on wave exposure. This example suggests a mechanism of population control where the impact of a physical factor on population size is larger at higher population density and supports early hypotheses about the occurrence of density-dependent population control by physical factors when the availability of safe sites is limiting.

KEY WORDS: Density dependence · Dislodgment · Intraspecific competition · Hummocking · Multilayering · Physical factors · Rocky shore · Space limitation

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Cite this article as: Gutiérrez JL, Palomo MG, Bagur M, Arribas LP, Soria SA (2015) Wave action limits crowding in an intertidal mussel. Mar Ecol Prog Ser 518:153-163.

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